Replacing metal and heavy parts with plastic parts is common. However, when the part takes on odd shapes or need structural strength replacement with plastic becomes more difficult. The use of fibers to reinforce the plastic is a common practice, with oriented fibers known to be stronger than unoriented fibers.
Affixing a thermoplastic material to a support structure is also known. For example, WO 03/102387 describes an oil pan for an internal combustion engine having a “shell of plastic material, and a support structure, having a plurality of perforations, that is fixedly attached to the exterior surfaces and/or the interior surfaces of the plastic shell.” p. 1, ¶1. However, the current methods to manufacture such articles are considered to provide for an article that is too heavy for use in applications, such as aircraft interiors, requiring lightweight articles that maintain high strength in areas that are prone to failure under stress.
One such challenging article is the seat frame used in airplanes. Seat frames must bear a large load. Imagine the frame locked to the floor, with a person sitting in it, and the person behind the seat grasping the seat and using it to assist lifting him or herself out of the seat. The amount of torque on the support or weakest spot of the frame is quite large.
Many have tried to make a seat back using thermoset composites reinforced with fibers. Thermoset composites are time consuming to process with low throughput and increased costs. Efforts to increase the time have resulted in increased weight of the final part, making it unappealing to the airline industry.
WO 2010 111700 published 30 Sep. 2010 discloses one method of incorporating oriented strength enhancing carbon fibers. This method used a pre-formed tube of the fibers in a thermoplastic matrix, expanded the tube in a heated mold allowing the thermoplastic to set up in the “U” shape of the seat back.
This method is expensive and overdesigns strength where strength is not needed.
There exists therefore the need for a method of manufacturing an article that is lightweight, and that maintains high strength in areas that are prone to failure under stress.